Wax removal from oil



Sept. 19, 1933.

J. A. ANDERSON 1,927,057

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John A. Anderson, Chicago, 111., assignonl to Standard Oil Company, Chicago, 111., a corporation of Indiana Application October 2, 1931. Serial No. 566,448

Claims. (Cl. 196-17) This invention relates to wax removal from oil high melting wax (135-140 F.) is a high boiling and it pertains more particularly to the removal wax, that is, it has a distillation range of about of wax from viscous petroleum lubricating oils 850l300 F. at atmospheric pressure. A low wherein the distillation range of the wax is subboiling wax, which is usually also a low melting 5 stantially the same as that of the oil. point wax, should have a distillation range enso It is essential that lubricating oils flow freely tirely below that of the high boiling wax. A low at low temperatures or, in other words, that the melting wax of 122-124 F. melting point has a oils have a low pour point. Usually wax-bearing distillation range of about GEO-800 F. at atmosoil is diluted with naphtha and chilled to cryspheric pressure and may therefore be considered separated from the diluted oil by filtration, set- F. m. p. wax. I prefer, however, to use a 105- tling, or centrifuging, etc. Acomplete wax sepa- 107 F. melting point wax for the low boiling ration cannot be obtained in this manner because wax.

wax is somewhat soluble in filter naphtha as well I do not limit myself to any theory or explanaas in oil. It has been proposed to use antition of how one wax is replaced by another. It 70 solvents for more effectively throwing the wax may be a phenomenon analagous to the law out of solution but this expedient isobjectionof mass action, the low boiling point wax tendable because of the unduly high expense, because ing to throw out and replace the high boiling of added risks due to inflammability and toxic point waxes in solution. I believe that the low properties of antisolvents and because of the fact boiling waxwhich is added in an amount pre- 175 that the antisolvents sometimes throw the oils ponderating over the amount of high boiling wax out of solution, thereby making the dewaxing remaining i t partially deWaXed Oil goes into operation very difficult. The object of my invensolution until an equilibrium is established for tion is to remove substantially all of the wax both waxes, depending on their relative proporfrom the oil without the use of wax antisolvents. tion and solubility. This process may be has- A further object is to decrease the cost equiptened by al ow t temperature to rise 80 that ment and labor required in the dewaxing of lubrithe added wax will dissolve in the oil, then chillcating oils. ing again to recrystallize both waxes together.

In practicing my invention I make use of the By increasing the proportion of added wax, the

30 fact that one wax may be replaced by another in Original wax can be almost entirely thrown out a solution of wax-in-oil or a wax in an oil-diluent of solution. What wax remains is obviously almixture. In any lubricating oil distillate, even at most entirely of the low boiling crystalline type low temperatures, there will be a certain amount which can be removed preferably by distillation of wax of the same distillation range in solution. because of its low boiling point.

35 The dissolved wax in heavy oil is of relatively My process is very simple: I dewax the oil at an high boiling point and in a light oil it is of relaeasily obtainable low temperature, add a large tively low boiling point. I have found that if amount of an entirely different wax (different disa large amount of a different wax is added to the tillation range), dewax again, and finally remove chilled mixture, some of the added wax will disthe remaining part of the added wax by distilla- 40 solve, and some of the dissolved wax will separate tion. If there are 101 parts of wax initially and .out. In other words, if a diluent-oil mixture con- I remove parts by the first rough dewaxing taining high boiling point wax is chilled to 0 F. step, I may add 100 parts of a lower boiling point and allowed to reach equilibrium, a certain wax (having lower boiling range) and repeat the amount of the wax will be in solution and the dewaxing step. In the second dewaxing step prac- 45 rest will crystallize out. If a low boiling wax is tically all of the original wax will be removed by 100 added to this chilled solution some of it will disfiltration and the dissolved wax in the final filtrate solve and at the same time some of the dissolved will consist largely of the low boiling point wax. high boiling wax will be thrown out of solution. This low boiling point wax can then be removed By substituting a wax of different distillation from the oil by simple distillation leaving a de- 50 range I have made it possible to effectively sepawaxed oil with an extremely low pour point,-a

rate the wax from oil by distillation and thereby pour point which is in fact lower than the temperobtain dewaxed oils of very low pour points. ature at which the oil was dewaxed (filtered).

The expressions W o and high boil- Ordinarily it is necessary to chill oil diluted with ing are used herein to differentiate between filter naphtha to 40 F. in order to obtain a 5 waxes of different distillation ranges. Usually a pour point of from +1 to 10 F. By using my improved process I may dewax at 0 F. and obtain a pour point of -5 to l() F.

My invention will be more clearly understood from the following detailed descriptions of preferred embodiments thereof, read in connection with the accompanying drawings, which form a part of this specification, wherein:

Figure 1 is a fiow sheet showing the addition of low boiling point wax to heavy oil.

Figure 2 is a flow sheet showing the addition of high boiling point wax to light oil, and.

Figure 3 is a flow sheet showing the process of combining the dewaxing of separate fractions to remove the wax more completely from each fraction.

In my preferred example I will describe the dewaxing of a Mid-Continent distillate having a viscosity at 100 F. of about 650 seconds Saybolt and a viscosity at 210 F. of about 60 seconds Saybolt. This distillate should be steam-refined and/or distilled under a partial vacuum so that decomposition is prevented. It should be understood, however, that my invention is applicable to any wax-bearing oil of any boiling point and viscosity range.

In accordance with the usual practice I dilute about one part of the wax-bearing oil (which has preferably been acid treated in the conventional manner) with four parts of diluent naphtha. I chill the diluted mixture to about 0 F. to crystallize out as much of the wax as possible and I mechanically separate the wax from the diluted oil by filtration (although I might also use settling or centrifuging). This step may be called the preliminary dewaxing and although most of the wax is removed, a portion of it remains dissolved in the diluted oil so that if the diluent were removed from the oil, the pour point would be from +15 to 25 F.

In practicing my invention I mix the diluted heavy oil from the preliminary dewaxing step with a low boiling point wax, the volume of the added wax being about equivalent to the volume of the wax removed by the preliminary dewaxing, which may be about 5-15% by weight of the original wax-bearing oil. In my preferred example the wax removed in the preliminary step may have a melting point of 135-140" F. and the low boiling point wax which I add to the diluted oil may have a melting point of about 105-107 F. To the mixture of diluted oil and low boiling point Wax I may add sufficient diluent to compensate for any diluent lost in the preliminary dewaxing step.

If the low boiling point wax is introduced into the diluted oil in liquid form, it is necessary to rechill the diluted mixture prior to the second wax separation. I therefore again chill to 0 F. and filter the wax crystals from the diluted oil, the wax being introduced into a still for recovery of diluent and fractionation of wax, and the diluted oil being introduced into another still. After the diluent is removed from the oil I raise the temperature thereof to distil off the low boiling point wax, which has a boiling point considerably below that of the oil. To insure the removal of this wax I prefer to distil over about 5% of the oil with the wax. The remaining oil is substantially wax-free and it has the unbelievably low pour point of -8 F. It may seem impossible to obtain a pour point lower than the dewaxing temperature, but this is accomplished by substituting a low boiling wax for the dissolved wax and finally removing the low boiling wax by distillation.

Where light (relatively low boiling) oils are to be dewaxed, it may be desirable to mix the diluted oil from the preliminary dewaxing with a high boiling wax. (See Figure 2.) The process is the same as that hereinabove described, except that after the diluent is removed from the final filtrate all of the oil is distilled except about 5 or 10%; in this case the wax remains in the residue and the distillate should be substantially wax-free. Practically, however, I find that it is more difiicult to separate added heavy wax than added light wax, and the embodiment shown in Figure 1 is preferred.

Ordinarily a refinery must dewax both light and heavy oils; in accordance with my invention I separate the oil in narrow fractions and I de wax them by the combination process described in Figure 3. Both of the fractions are subjected to a separate preliminary dewaxing. Low boiling point wax obtained from the light fraction is added to the diluted heavy oil and high boiling point wax obtained from the heavy fraction is added to the diluted light oil. Both oils are then subjected to a second dewaxing, diluent is removed from the separate oil fractions, the low boiling point wax is separated from the heavy oil and the light oil is separated from the high boiling point wax. The dewaxed oil fractions may then be used separately or they may be united and in either case a lower pour point is obtained than would be obtainable by the dewaxing of the oil in a single fraction.

No definite figures can be given as to the distinction between high boiling and low boiling waxes but the difference between the distillation range of the wax in the diluted oil and the added wax should be as great as is practically possible, because the degree of dewaxing is dependent in part at least upon the final separation of oil from added wax by distillation, but if the boiling point of the added wax is sufiiciently different from the boiling point of the oil so that these components may be separated by distillation, substantially complete dewaxing may be accomplished without the use of antisolvents and without the extremely low chilling temperatures which have heretofore been deemed imperative.

While I have disclosed the use of filter naphtha, it should be understood that my invention is equally applicable to dewaxing with other diluents, such as butane, propane or pentane. The refrigeration may be accomplished by indirect cooling or by the direct expansion of propane or butane. Various proportions of diluent may be used and the amount of wax added to the diluted oil may vary within relatively wide limits, preferably from about 5 to 25%. While I have described in detail a preferred embodiment of my invention, it is understood that I do not limit myself thereto, except as defined by the following claims which should be construed as broadly as the prior art will permit.

I claim:

1. The method of separating dissolved wax wax has a lower boiling point than the dissolvedwax.

3. The method of separating dissolved wax from a viscous hydrocarbon oil of narrow boiling range which comprises, diluting the oil with a light hydrocarbon diluent, adding a wax of different boiling range, chilling the-mixture to pre- *adding a wax of difierent properties to replace a large part of the waxwhich remains dissolved in the diluted oil, chilling said added wax to cause the precipitation thereof together with the precipitation of most of the wax previously in solution, separating the precipitated wax from the diluted oil, distilling said diluent from. said oil, and separating by distillation the finishedoil from added wax dissolved therein. t

6. The method of removing wax from a viscous hydrocarbon lubricating oil of substantially the same boiling range which comprises, replacing a part of said wax by a wax of diflerent boiling range and removingsaid wax of diflerent boiling range therefrom by distillation.

V 7. The method of removing wax from a viscous hydrocarbon lubricating oil of substantially the same boiling range which comprises, adding a wax of difl'erent boiling range, diluting and chilling said oil and wax to a low temperature to effect precipitation of waxrseparating the precipitated wax from the diluted; oil, and lation a large portion of the wax dissolved in the diluted oil whereby the finished oil has a pour point lower than the chilling temperature 8. The method of removing wax from a viscous petroleum lubricating oil of substantially the same boiling range which comprisesfdiluting, chilling, mechanically separating crystallized wax from the oil, adding a wax of different boiling range to the oil from which crystallized wax has been removed, mechanically removing a portion of said added wax together with a large portion of dissolved wax which is thrown out of solution thereby and finally distilling the finished oil to remove the diluent and the wax of different boiling range therefrom. 9. The method of removing dissolved wax from a lubricating oil of substantially the same boiling range which comprises, separating said oil into light and heavy fractions, subjecting both fractions to preliminary dewaxing, adding the wax obtained from the light fraction to the heavy oil and the wax obtained from the heavy fraction to the light oil, separately chilling and filtering the respectivefractions, distilling the low boiling point wax from the finished heavyoil fraction and distilling the finished light oil fraction from the high-boiling point wax residue.

10. The-combination of claim 9 wherein the fractions are united to give a dewaxed oil of intermediate viscosity.

, JOHN A. ANDERSON.

removing by distil- I 

